Some supporters, one of whom appeared to be using a megaphone, shouted sentences including: "Zieler, why don't you kill yourself?" and "Your mother is related to [former Germany keeper Robert] Enke," with the shouts clearly audible on TV.

Former Germany keeper Enke took his own life in 2009, having suffered from depression for many years.

And speaking to reporters following a J-League match for Vissel Kobe, former Cologne star Podolski said: "As pros we must live with insults. But what happened in Cologne, referring to Enke, is unacceptable. We can't tolerate this."

Cologne said on their official website that they have started banning procedures against two people, who could now face a stadium ban. "Neither the fans nor the ultras are responsible for the chants," the club said.

German FA (DFB) president Reinhard Grindel called for a clampdown as the organisation opened an investigation into what happened.